Measurements of Quarkonium Production and Polarization at CMS

The polarizations of Y(nS) (n=1,2,3) and prompt J/\psi and \psi(2S), as well as the differential cross section of the Y(nS), are measured in proton-proton collisions at sqrt(s) = 7 TeV, using a dimuon data sample collected by the CMS experiment at the LHC, corresponding to an integrated luminosity of 4.9 fb-1. The differential cross section is measured as a function of transverse momentum of Y(nS). The data show a transition from exponential to power-law behavior in the neighborhood of 20 GeV, and the power-law exponents for all three states are consistent. The polarization parameters \lambda\theta, \lambda\phi, and \lambda\theta\phi, as well as the frame-invariant quantity \lambda, are measured from the dimuon decay angular distributions in three different polarization frames. No evidence of large polarizations is seen in these kinematic regions, which extend much beyond those previously explored.Comment: to appear in the proceedings of The 6th International Workshop on Charm Physics (CHARM 2013

Measurements of Quarkonium production and polarization at CMS

Studies of quarkonium production and polarization play an important role in understanding QCD. CMS has recently measured the $\Upsilon$(nS) (n=1,2,3) production cross sections and polarizations, as well as the prompt $\psi$(nS) (n=1,2) polarizations, using a dimuon sample collected in proton-proton collisions in 2011 at $\sqrt{s} =$ 7 TeV. The differential cross sections of the $\Upsilon$(nS) states are presented as a function of dimuon transverse momentum, covering a wide range of $p_\mathrm{T}$ (10--100 GeV). All three states show a similar behaviour and display a change of shape from an exponential to a power-law at $p_\mathrm{T} \approx$ 20 GeV. The polarizations of the $\Upsilon$(nS) and $\psi$(nS) states are determined in bins of dimuon transverse momentum and rapidity, significantly extending the $p_\mathrm{T}$ and rapidity ranges probed by previous experiments. The experimental measurements are in disagreement with current theoretical predictions